This invention generally relates to the authentication of passive entry and start devices. More particularly, this invention relates to the calculation of encrypted information utilized for authentication of remote identification devices.
Passive and active entry and start devices communicate with a module within a motor vehicle to authorize and perform desired functions remotely. Such functions include, for example, unlocking of the motor vehicle and enabling the starting system without a mechanical key. In order to prevent unauthorized access, the module and remote devices utilize an encryption that is utilized to confirm the authenticity of the remote device. Many such encryption methods and calculations are known and utilized. All such methods require time for the calculations to be performed. Further, in most systems, more than one authentication device such as a key fob are authorized for operation of a single vehicle. Accordingly, a separate unique authentication is required for each of the different authentication devices. Again, increasing potential wait times until operation is authorized.
In one example, a passive authentication device begins communication upon some physical prompt, such as actuation of a vehicle door handle. Upon this action, the vehicle module sends out a low frequency radio signal and then waits for a reply from proximate authentication devices. In one example system, each authentication device transmits at a predefined time. The absence of a signal at a predefined time after the LF signal indicates that that particular authentication device is not in the area. Once, the time for reply for all of the authentication devices have past, cryptology calculations for the authentication device present are performed. The cryptology calculations generate a unique encrypted message that prevents unauthorized access to vehicle functions. Such calculations can contribute to a perceptible wait period where a perception of an immediate response and actuation are desired.
Accordingly, it is desirable to design and develop an encryption calculation system and method that substantially reduces or eliminates any perceived hesitation in system response.